High rate gravel packing

ABSTRACT

A method of gravel packing a portion of a cased wellbore proximate perforations by using coiled tubing is disclosed. The portion of the wellbore containing perforations is isolated from the portion of the wellbore below the perforations. A connection apparatus is installed between a bottom hole assembly and the coiled tubing and this connection apparatus comprises a crossover tool. The bottom hole assembly is lowered into the wellbore using the coiled tubing until the bottom hole assembly is proximate the perforations. Then, a slurry comprising a gravel and a carrier fluid is pumpdown the coiled tubing and into the annulus between the coiled tubing and the casing. A second fluid which is compatible with the slurry is pumpdown the annulus between the coiled tubing and the casing while the slurry is above the connection apparatus between the bottom hole assembly and the coiled tubing. The second fluid and the slurry mixture reduce the slurry concentration prior to reaching the perforations.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of the filing date of U.S. Provisional Patent Application No. 60/943,114 filed Jun. 11, 2007.

TECHNICAL FIELD

The present invention relates generally to recovery of hydrocarbons in subterranean formations, and, more particularly, to tools, systems and methods for performing a gravel packing operations in a wellbore.

BACKGROUND OF THE INVENTION

When well fluid is produced from a subterranean formation, the well fluid typically contains particulates, which are commonly referred to as “sand.” The production of sand from the well must be controlled in order to extend the life of the well. One technique to accomplish this control involves routing the well fluid through a downhole filter formed from gravel that surrounds a sandscreen. A typical sandscreen comprises a cylindrical mesh that is inserted into and that is generally concentric with the borehole of the well where the fluid is to be produced. Gravel is packed in the area between the formation and the sandscreen, and that area is called the “annulus.” The well fluid being produced passes through the gravel, enters the sandscreen, and is communicated uphole via tubing that is connected to the sandscreen.

The gravel that surrounds the sandscreen typically is introduced into the well in a gravel packing operation. In a conventional gravel packing operation, the gravel is communicated downhole via a slurry, which is a mixture of a carrier fluid and gravel. A gravel packing system in the well directs the slurry into the annulus, and the carrier fluid disperses into the formation or passes through the sandscreen to be returned to the earth's surface. The gravel, on the other hand, remains packed between the sandscreen and the formation.

When performing a Thru Tubing Gravel Pack (TTGP) operation using coiled tubing (or any relatively small-sized tubing), sufficient perforations packing is usually an issue, thus leading to a high skin. In view of the limited pumping rate that can be realized through coiled tubing, good perforations packing may not be obtained and it may not be possible to break down the formation, which is required for carrying out a High Rate Water Pack (HRWP) or Frac Pack.

An alternative solution may be to pump the slurry (containing carrier fluid and proppants) through the annulus or simultaneously through the annulus and coiled tubing to achieve this high rate. Pumping the slurry while the coiled tubing is still in the hole may, however, result in screening out above the coiled tubing (i.e., where proppants settle at a level above the coiled tubing connection to the bottom hole assembly (BHA)) and thus get the coiled tubing stuck in the hole.

Yet another alternative solution is to utilize a sandscreen operation where the coiled tubing is retrieved and the Gravel Pack/Frac Pack pumping operation is performed down tubing. When utilizing this operation, a coiled tubing run as to be carried out to clean out the proppants before putting the well back into production. This method has its limitations in terms of drawdown and the deviation at the zone of interest.

TTGP techniques are described in SPE 72132, “Effective Thru Tubing Gravel Pack Methods in Attaka Field” by C. C. Lee et al., October 2001. That paper describes two techniques for TTGP, including: (1) TTGP with Packoff Method; and (2) TTGP with Vent Screen Method.

The Packoff Method employs a TTGP sandscreen with a blank spacer pipe and packoff the seal assembly that can be placed inside casing or an existing gravel act sandscreen, spaced out, and packed off inside the production tubing. A potential problem with this technique is that pumping may be performed at a lower rate since the pumping is performed through a coiled tubing, and this may yield poor perforation packing and thus unsatisfactory job results.

The Vent Screen Method employs two sandscreen sections that are separated by blank pipe placed and packed in the casing with production entering the lower section of sandscreen and exiting the upper section of the sandscreen. A potential problem with this technique is that it has a limited field of applications and generally may not be used for operations inside tubings or in reservoirs with high deviation angles.

Accordingly, a need exists for an improved method of performing a TTGP operation. That objective has been realized by the present invention.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method of gravel packing a portion of a cased wellbore proximate perforations by using coil tubing is provided which comprises the steps of isolating the portion of the wellbore containing the perforations from the portion of the wellbore below the perforations. A connection apparatus is then installed between a bottom hole assembly and the coiled tubing and the bottom hole assembly is then lowered into the wellbore using the coiled tubing until the bottom hole assembly is proximate the perforations.

The method of the present invention further comprises pumping a slurry down the coiled tubing and into the annulus between the coiled tubing and the casing, wherein the slurry comprises gravel and a carrier fluid. A second fluid which is compatible with the slurry is pumped down the annulus between the coiled tubing and the casing while the slurry is above the connection between the bottom hole assembly and the coiled tubing. The slurry and the second fluid mix, prior to reaching the perforations, and form a homogeneous solution with a reduced the slurry concentration.

In one embodiment of the present invention, the connection apparatus between the bottom whole assembly and the coiled tubing includes a crossover tool which has pumping and non-pumping positions. The step of pumping the slurry down the coiled tubing comprises the step of shifting the crossover tool from the non-pumping to the pumping position. In one embodiment, the step of shifting the crossover tool from the non-pumping to the pumping position comprises dropping a ball down the coiled tubing at the earth's surface.

In one embodiment of the present invention, the slurry and the second fluid are designed to flow at a rate sufficient to break down the formation proximate the perforations. In this embodiment, the slurry may comprise proppants.

A method according to the present invention further comprises the step of removing the coiled tubing and the connection device once a wellbore screenout has been obtained. Thereafter, a method according to the present invention comprises the step of installing a sealing apparatus above the gravel pack bottom hole assembly. In one embodiment, the step of installing a sealing apparatus comprises the installation of a packer above the gravel pack bottom hole assembly. In another embodiment, the step of installing a sealing apparatus comprises the installation of a pack-off assembly above the gravel pack bottom hole assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1-3, 3A-B, and 4-6 are elevation drawings which illustrate the various steps of a method in accordance with the present invention for gravel packing a cased wellbore.

DESCRIPTION OF SPECIFIC EMBODIMENTS

It will be appreciated that the present invention may take many forms and embodiments. In the following description, some embodiments of the invention are described and numerous details are set forth to provide an understanding of the present invention. Those skilled in the art will appreciate, however, that the present invention may be practiced without those details and that numerous variations and modifications from the described embodiments may be possible. The following description is thus intended to illustrate and not to limit the present invention.

With reference first to FIG. 1, a wellbore 10 contains casing 11 which has been secured in place with cement 13. Perforations 12 have been made through the casing 11 and cement 13 and into the producing formation. The zone of the wellbore 10 containing perforations 12 is isolated from zones of the wellbore below perforations 12 by using isolation device 14, which may, for example, comprise a bridge plug or a packer.

Bottom Hole Assembly 15, which comprises a sandscreen, is lowered into the wellbore by utilizing coiled tubing 16. Coiled tubing 16 is operatively connected to Bottom Hole Assembly 15 by connection device 17 which may, for example, comprise a hook-up nipple having a crossover device. Connection device 17 may, however, comprise any suitable tubing connect/disconnect tool having a crossover device.

Referring now to FIGS. 1-3, the Bottom Hole Assembly 15 is lowered into the casing 11 until isolation device 14 is reached. Centralizing elements 18 are provided to assure that the Bottom Hole Assembly 15 remains concentric with the casing 11. As the Bottom Hole Assembly 15 is lowered into the casing 11 in wellbore 10, the crossover tool in connection device 17 is in a closed or non-pumping position, as illustrated in FIG. 3A.

With reference to FIGS. 2 and 3, once the Bottom Hole Assembly 15 reaches final depth the connection device 17 is shifted from the non-pumping position (FIG. 3A) to a pumping position (FIG. 3B) by utilizing drop ball 19 which is launched down the coiled tubing 16 from the earth's surface. After drop ball 19 has landed in connection device 17, the coiled tubing 16 may be pressured up to cause the connection device 17 to shift to the pumping position. The coiled tubing 16 is a weighted down to prevent releasing the connection device 17 and pumping inside the gravel pack bottom hole assembly.

In some embodiments of the present invention, injection tests may be conducted at this point to measure formation breakdown and frac extension before spotting gravel pack carrier fluid on the backside of the annulus. This fluid may later serve as a pad fluid for the HRWP or Frac Pack (or other hydraulic fracturing or fracing operation). A space may be pumped behind us at fluid and followed by a breaker, which is squeezed ahead of the carrier fluid into the formation. In some cases, a hydraulic fracturing operation involves pumping a proppant-free come up viscous fluid (sometimes called a “pad fluid”) into the formation at a rate higher than the fluid can escape into the formation so that the pressure in the formation rises and formation brakes creating a new fracture or enlarging a natural fracture.

With reference now to FIG. 4, slurry 20 is pumped down the coiled tubing 16, and slurry 20 may, for example, have a concentration of 0.5 to 4 ppa. With slurry 20 above the crossover tool in connection device 17, a clean fluid or sand free solution 21 is pumped down the annulus between the coiled tubing 16 and the casing 11. This clean fluid or sand-free solution 21 may, for example, comprise gravel pack carrier fluid or compatible brine. In some embodiments, both fluid streams, i.e., the one down the coiled tubing 16 and the one within the annulus between the coiled tubing 16 and the casing 11, may be designed to flow at a rate sufficient to break down the formation and thereby carry out a HRWP or Frac Pack.

The slurry 20 exits the crossover port of connection device 17 in the region designated by the oval 22 in FIG. 4. Once that occurs, the slurry 20 will mix with the compatible solution 21 which is being pumped down the annulus and effectively reduce the slurry concentration, for example from 0.5 to 4.0 ppa to 0.2 to 2 ppa. The mixture 27 of the slurry 20 and the compatible solution 21 will then enter the perforations 12 as illustrated by arrows 23 in FIG. 4. In one embodiment, the mixture 27 is a homogeneous solution. The annular space 29 between the sandscreen in Bottom Hole Assembly 15 will then be packed as in a regular gravel pack operation.

Once a wellbore screenout has occurred (as illustrated in FIG. 5), the remaining slurry will be circulated out of the wellbore by pumping it down the coiled tubing 16 and taking returns 24 via the annulus between the casing 11 and the coiled tubing 16 area.

Turning now to FIG. 6, once the wellbore is clean of remaining proppant, the coiled tubing 16 and the connection device 17 with a crossover port are pulled out of the casing 11 leaving the gravel packed Bottom Hole Assembly 15 installed downhole. In some embodiments, a slickline run may be performed to insure that the connection device 17 is clean of proppant, before installing a sealing mechanism 26 which may, for example, comprise a packer or a pack-off assembly. The sealing mechanism 26 ensures that the proppants placed around this sandscreen in the Bottom Hole Assembly 15 cannot be produced back to the surface together with hydrocarbons 25.

In some aspects of the present invention the coiled tubing collapse pressure should not be exceeded in order to avoid potential problems while carrying out the method of the present invention. At the same time, the coiled tubing should remain in position to avoid pumping the crossover connector out of the connection device 17. Movement calculations with respect to casing 11 may need to be carried out to avoid this, which could lead to placing proppant inside the sandscreen in the Bottom Hole Assembly 15. 

1. A method of gravel packing a portion of a cased wellbore proximate perforations by using coiled tubing, comprising the steps of: isolating the portion of the wellbore containing perforations from the portion of the wellbore below the perforations; installing connection apparatus between a bottom hole assembly and the coiled tubing; lowering the bottom hole assembly into the wellbore using the coiled tubing until the bottom hole assembly is proximate the perforations; pumping a slurry comprising gravel and a carrier fluid down the coiled tubing and into the annulus between the coiled tubing and the casing; and pumping a second fluid which is compatible with the slurry down the annulus between the coiled tubing and the casing while the slurry is above the connection between the bottom hole assembly and the coiled tubing, so that the second fluid and the slurry mix to form a solution with a reduced slurry concentration prior to reaching the perforations.
 2. The method of claim 1, wherein the connection between the bottom hole assembly and the coiled tubing includes a crossover tool having pumping and non-pumping positions and the step of pumping the slurry down the coiled tubing comprises the step of shifting the crossover tool from the non-pumping to a pumping position.
 3. The method of claim 2, wherein the step of shifting the crossover tool from the non-pumping to the pumping position comprises dropping a ball down the coiled tubing at the earth's surface.
 4. The method of claim 1, wherein the slurry and the second fluid are designed to flow at a rate sufficient to break down the formation proximate the perforations.
 5. The method of claim 4, wherein the slurry comprises proppants.
 6. The method of claim 1, wherein the slurry comprises a concentration of about 0.5 to 4.0 ppa and the mixture of the slurry and the second fluid comprises a concentration of about 0.2 to 2.0 ppa.
 7. The method of claim 1, further comprising the step of circulating out the slurry by pumping it down the coiled tubing and taking returns of the slurry via the annulus between the coiled tubing and the casing, once a wellbore screenout has been obtained.
 8. The method of claim 1, further comprising the step of removing the coiled tubing and the connection device from the wellbore.
 9. The method of claim 8, further comprising the step of installing a sealing apparatus above the gravel packed bottom hole assembly.
 10. The method of claim 9, wherein the step of installing a sealing apparatus comprises the installation of a packer above the gravel packed bottom hole assembly.
 11. The method of claim 9, wherein the step of installing a sealing apparatus comprises the installation of a pack-off assembly above the gravel packed bottom hole assembly.
 12. A method of gravel packing a portion of a cased wellbore proximate perforations by using coiled tubing, comprising the steps of: installing a scaling device in the wellbore to isolate the portion of the wellbore containing perforations from the portion of the wellbore below the perforations; installing connection apparatus between a bottom hole assembly and the coiled tubing, where the connection apparatus comprises a crossover tool having pumping and non-pumping positions; lowering the bottom hole assembly into the wellbore using the coiled tubing until the bottom hole assembly is proximate the perforations; shifting the crossover tool from the non-pumping to the pumping position; pumping a slurry comprising gravel and a carrier fluid down the coiled tubing and into the annulus between the coiled tubing and the casing; and pumping a second fluid which is compatible with the slurry down the annulus between the coiled tubing and the casing while the slurry is above the connection apparatus between the bottom hole assembly and the coiled tubing, so that the second fluid and the slurry mix to form a solution with reduced slurry concentration prior to reaching the perforations.
 13. The method of claim 12, wherein the slurry and the second fluid are designed to flow at a rate sufficient to break down the formation proximate the perforations.
 14. The method of claim 12, wherein the step of shifting the crossover tool from the non-pumping to the pumping position comprises dropping a ball down the coiled tubing at the earth's surface.
 15. The method of claim 12, wherein the slurry comprises a concentration of about 0.5 to 4.0 ppa and the mixture of the slurry and the second fluid comprises a concentration of about 0.2 to 2.0 ppa.
 16. The method of claim 12, further comprising the step of circulating out the slurry by pumping in down the coiled tubing and taking returns of the slurry via the annulus between the coiled tubing and the casing, once a wellbore screenout has been obtained.
 17. The method of claim 12, further comprising the step of removing the coiled tubing and the connection apparatus from the wellbore.
 18. The method of claim 17, further comprising the step of installing a sealing apparatus above the gravel packed bottom hole assembly.
 19. The method of claim 18, wherein the step of installing a sealing apparatus comprises the installation of a packer above the gravel packed bottom hole assembly.
 20. The method of claim 18, wherein the step of installing a sealing apparatus comprises the installation of a pack-off assembly above the gravel packed bottom hole assembly. 